Getting undefind variable error & don't konw how to fix

Question

****警告：/var/www/html/magento2/app/code/Custom/HelloWord/Controller/Hello/Event.php 中的未定义变量 $item ** **`

<?php

namespace Custom\HelloWord\Controller\Hello;

class Event extends \Magento\Framework\App\Action\Action
{

    public function execute()
    {
        $textDisplay = new \Magento\Framework\DataObject(array('text' => 'Custom'));
        $this->_eventManager->dispatch('sales_quote_remove_item', ['quote_item' => $item]);
        echo $textDisplay->getText();
        exit;
    }
}`